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  <h1 class="topictitle1">queue_node Template Class</h1>
 
   
  <div> 
	 <div class="section"><h2 class="sectiontitle">Summary</h2> 
		 
		<p>An unbounded buffer of messages of type T. Messages are forwarded in
		  first-in first-out (FIFO) order. 
		</p>
 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Syntax</h2> 
		 
		<pre>template &lt;typename T, typename A = cache_aligned_allocator&lt;T&gt; &gt;
class queue_node;</pre> 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Header</h2> 
		 
		<pre>#include "tbb/flow_graph.h"</pre> 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Description</h2> 
		 
		<p>A 
		  <span class="keyword">queue</span><span class="keyword">_node</span> is a 
		  <span class="keyword">graph_node</span>, 
		  <span class="keyword">receiver&lt;T&gt;</span> and 
		  <span class="keyword">sender&lt;T&gt;</span> that forwards messages in first-in
		  first-out (FIFO) order to a single successor in its successor set. Successors
		  are tried in the order that they were registered with the node. If a successor
		  rejects the message, it is removed from the successor list as described by the
		  policy in the Message Passing Protocol, and the next successor in the set is
		  tried. This continues until a successor accepts the message, or all successors
		  have been attempted. Items that are successfully transferred to a successor are
		  removed from the buffer. 
		</p>
 
		<p>A 
		  <span class="keyword">queue_node</span> is reservable and supports a single
		  reservation at a time. While the 
		  <span class="keyword">queue_node</span> is reserved, no other items will be
		  forwarded to successors and all 
		  <span class="keyword">try_get</span> calls will return 
		  <span class="keyword">false</span>. While reserved, 
		  <span class="keyword">try_put</span> will still return 
		  <span class="keyword">true</span> and add items to the 
		  <span class="keyword">queue_node</span>. 
		</p>
 
		<p>An allocator of type 
		  <span class="keyword">A</span> is used to allocate internal memory for the 
		  <span class="keyword">queue_node.</span> 
		</p>
 
		<p><span class="keyword">T</span> must be copy-constructible and assignable. 
		</p>
 
		<p>Rejection of messages by successors is handled using the protocol in
		  the Message Passing Protocol, see link below. 
		</p>
 
	 </div>
 
	 <div class="section"><h2 class="sectiontitle">Members</h2> 
		 
		<pre>namespace tbb {
namespace flow {
 
 
template &lt;typename T, typename A = cache_aligned_allocator&lt;T&gt; &gt;
class queue_node :
  public buffer_node&lt;T, A&gt; {
public:
    queue_node( graph &amp;g );
    queue_node( const queue_node &amp;src );
 
    // receiver&lt;T&gt;
    typedef T input_type;
    typedef sender&lt;input_type&gt; predecessor_type;
    bool try_put( const input_type &amp;v );
    bool register_predecessor( predecessor_type &amp;p );
    bool remove_predecessor( predecessor_type &amp;p );
 
    // sender&lt;T&gt;
    typedef T output_type;
    typedef receiver&lt;output_type&gt; successor_type;
    bool register_successor( successor_type &amp;r );
    bool remove_successor( successor_type &amp;r );
    bool try_get( output_type &amp;v );
    bool try_reserve( output_type &amp;v );
    bool try_release( );
    bool try_consume( );
};
 
}
}</pre> 
		
<div class="tablenoborder"><table cellpadding="4" summary="" frame="border" border="1" cellspacing="0" rules="all"><span class="tabledesc">The following table provides additional information on the
			 members of this template class. 
		  </span><thead align="left"> 
				<tr> 
				  <th class="cellrowborder" valign="top" width="33.89830508474576%" id="d81298e194">Member 
				  </th>
 
				  <th class="cellrowborder" valign="top" width="66.10169491525423%" id="d81298e197">Description 
				  </th>
 
				</tr>
</thead>
 
			 <tbody> 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">queue_node( graph &amp;g
						)</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>Constructs an empty 
						<span class="keyword">queue_node</span> that belongs to the 
						<span class="keyword">graph g</span>. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">queue_node( const queue_node
						&amp;src )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>Constructs an empty 
						<span class="keyword">queue_node</span> that belongs to the same 
						<span class="keyword">graph g</span> as 
						<span class="keyword">src</span>. The list of predecessors, the list of
						successors and the messages in the buffer are NOT copied. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">bool try_put( const input_type
						&amp;v )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>Adds 
						<span class="keyword">v</span> to all successors. 
					 </p>
the 
					 <span class="keyword">queue_node</span>. If 
					 <span class="keyword">v</span> is the only item in the 
					 <span class="keyword">queue_node</span> , a task is spawned to forward
					 the item to a successor. 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span>. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">bool register_predecessor(
						predecessor_type &amp;p )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>Never rejects puts and therefore does not need to maintain a
						list of predecessors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">false</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">bool remove_predecessor(
						predecessor_type &amp;p )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>Never rejects puts and therefore does not need to maintain a
						list of predecessors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">false</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">bool register_successor(
						successor_type &amp;r )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>Adds 
						<span class="keyword">r</span> to the set of successors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">bool remove_successor(
						successor_type &amp;r )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>Removes 
						<span class="keyword">r</span> from the set of successors. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">bool try_get( output_type &amp;v
						)</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if an item can be removed from the
						front of the 
						<span class="keyword">queue_node</span> and assigned to 
						<span class="keyword">v</span>. Returns 
						<span class="keyword">false</span> if there is no item currently in the
						
						<span class="keyword">queue_node</span> or if the node is reserved. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">bool try_reserve( output_type
						&amp;v )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>If the call returns 
						<span class="keyword">true</span>, the node is reserved and will
						forward no more messages until the reservation has been released or consumed. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if there is an item in the 
						<span class="keyword">queue_node</span> and the node is not currently
						reserved. If an item can be returned, it is assigned to 
						<span class="keyword">v</span>. Returns 
						<span class="keyword">false</span> if there is no item currently in the
						
						<span class="keyword">queue_node</span> or if the node is reserved. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">bool try_release( )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>Release the reservation on the node. The item that was
						returned in the last successful call to 
						<span class="keyword">try_reserve</span> remains in the 
						<span class="keyword">queue_node</span>. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if the node is currently reserved and
						
						<span class="keyword">false</span> otherwise. 
					 </p>
 
				  </td>
 
				</tr>
 
				<tr> 
				  <td class="cellrowborder" valign="top" width="33.89830508474576%" headers="d81298e194 "><span class="keyword">bool try_consume( )</span> 
				  </td>
 
				  <td class="cellrowborder" valign="top" width="66.10169491525423%" headers="d81298e197 "> 
					 <p>Releases the reservation on the 
						<span class="keyword">queue_node</span>. The item that was returned in
						the last successful call to 
						<span class="keyword">try_reserve</span> is popped from the front of
						the queue. 
					 </p>
 
					 <p><strong>Returns</strong>: 
						<span class="keyword">true</span> if the 
						<span class="keyword">queue_node</span> is currently reserved and 
						<span class="keyword">false</span> otherwise. 
					 </p>
 
				  </td>
 
				</tr>
 
			 </tbody>
 
		  </table>
</div>
 
	 </div>
 
  </div>
 
  
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong>&nbsp;<a href="../../reference/flow_graph.htm">Flow Graph</a></div>
</div>
<div class="See Also">
<h2>See Also</h2>
<div class="linklist">
<div><a href="message_passing_protocol.htm">Message Passing Protocol 
		  </a></div></div>
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